Ethylene glycol is a chemical which has found wide use in industry. It is used, for example in the preparation of plasticizers for vinyl polymers and as a component in polyester fibers and antifreeze formulations. In view of its many uses, there is a need to find new and more economical methods for preparing ethylene glycol.
Proposed methods for making ethylene glycol involve the reaction of carbon monoxide with hydrogen in the presence of various proposed catalyst systems at elevated temperatures and pressures. For example, one of the earliest disclosed processes for making polyhydroxy compounds from readily available and inexpensive starting materials such as formaldehyde, carbon monoxide and hydrogen was disclosed in U.S. Pat. No. 2,451,333. The process comprised heating the starting materials with a reduced cobalt oxide hydrogenation catalyst under a high pressure, in excess of 100 atm. and at a temperature from about 80.degree. C. to 300.degree. C. Actually the examples in this patent used high pressures in the range of 500-800 atmospheres.
In Japan Kokai No. 76,128,903 (1976) to Mitsubishi a procedure is disclosed for preparing ethylene glycol by the reaction of CO, H.sub.2 and HCHO with a cobalt catalyst containing a trivalent P, As or Sb compound at a temperature of about 160.degree. C. and a pressure of about 180 Kg/cm.sup.2, or approximately 2700 psi.
Similarly U.S. Pat. No. 4,144,401 uses CO, H.sub.2 and formaldehyde as starting materials, but they are reacted in the presence of an alcohol solvent and a catalytic amount of rhodium or a rhodium-containing compound at a moderate temperature and pressure. Of course use of rhodium in a catalyst makes it expensive for commercial purposes. Methanol is also produced in substantial amounts in this process.
U.S. Pat. No. 4,356,332 pertains to the production of ethylene glycol by reaction of formaldehyde with carbon monoxide and hydrogen in the presence of a catalyst comprising a cobalt-containing compound and a tin-or germanium-containing promoter and in the presence of a substantially inert, oxygenated hydrocarbon solvent.
In U.S. Pat. No. 4,200,765 there is disclosed a process for preparing glycol aldehyde by reacting formaldehyde, hydrogen and carbon monoxide in an aprotic solvent at elevated temperatures and superatmospheric pressures in the presence of a rhodium catalyst with subsequent conversion of the glycol aldehyde to ethylene glycol by hydrogenation.
Japan Kokai No. 82,118,527 (1981) to Mitsubishi discloses the use of a ruthenium-based catalyst with a trivalent phosphorous compound to convert formaldehyde, CO and H into ethylene glycol. The selectivity to ethylene glycol is not specified.
Japan Kokai No. 82,130,940 (1981) to Mitsui Petrochemicals employs a rhodium compound and an alkali metal compound. Again selectivity to ethylene glycol is not specified.
In U.S. Pat. No. 4,362,820 only carbon monoxide and hydrogen, without formaldehyde are used as starting materials for conversion to ethylene glycol via a catalyst comprising a cobalt-containing compound and a large excess of organosilicon compound. In most of the examples an operating temperature range of 250.degree.-270.degree. C. is employed, coupled with pressures of about 4000-8000 psi. Weight ratios of ethylene glycol to methanol were typically Ca. 2:1. Here selectivity to glycol cannot be calculated because only the yields of MeOH and glycol are specified.
Additional Japanese applications disclose the use of a solution of formalin, carbon monoxide and hydrogen to produce ethylene glycol in the presence of a cobalt catalyst. See Japanese Application No. 197909 to Agency of Ind. Sci. Tech. In Jap. Application No. 188137 to the same agency, ethylene glycol is produced by reacting CO and hydrogen optionally with formaldehyde in the presence of a cobalt carbonyl and a phenol and/or alkylphenol.
Japanese Application No. 004782 (1981) to Mitsubishi discloses a process for producing ethylene glycol from formaldehyde, CO and H.sub.2 in the presence of a catalyst containing ruthenium and a trivalent organo-phosphorous compound.
Finally in Japan Kokai Tokyo Koho JP No. 57,130,933 to Mitsubishi, acetals are reacted with CO and H in the presence of a cobalt-iodine catalyst system to produce ethylene glycol.
Many of these processes require the use of high pressures (particularly in the absence of an added formaldehyde source), some use expensive rhodium-containing compounds, in most the selectivities for ethylene glycol are not very substantial, and there is difficulty in separation of the glycol products from the selected solvent.
The disclosure of a process for producing ethylene glycol from simple starting materials such as syngas (i.e. carbon monoxide and hydrogen) and formaldehyde or paraformaldehyde by reacting the starting materials in the presence of a catalyst compound which would be relatively inexpensive even on a commercial scale, where reaction could be conducted at low temperatures and pressures, which would provide for better selectivity to desired ethylene glycol and its derivatives, and which would allow for ease of separation of glycol products from the solvent would be an advance in the art.